The goals of this continuing project are 1. Aim 1. To describe the course of differential brain aging vyith a focus on the best-case-scenario naturalistic study of successful aging. With that focus, the study will complement existing large-scale longitudinal investigations of typical geriatric samples. Our objective is to examine the closest approximation to successful physiological aging to be found in an unselected human population. 2. Aim 2, To gain insights into mechanisms of age-related differential brain shrinkage by examining changes in microstructure of the white matter and indirect indices of regional brain iron content. 3. Aim 3. To evaluate the links between age-related regional brain changes (volume, diffusion and magnetization properties, and iron content) and performance in three cognitive domains with known vulnerability to aging: episodic memory, executive functions, and speed of processing. 4. Aim 4. To examine the effect of vascular risk factors (physiological and genetic) as modifiers of brain and cognitive aging. We will continue our investigation into the effects of sub-clinical levels of vascular risk conveyed by elevated blood pressure, circulating cardiac risk factors (homocysteine, C-reactive protein), elevated insulin, and genetic variants associated with vascular and metabolic risk (MTHFR C677T, IL1-p C511T, BDNF Val66Met, ACE l/D, ApoEpound4, diabetes risk genes, and polymorphisms related to specific neurotransmitters - acetylcholine, serotonin, dopamine). Aim 5. Common to all listed aims is a longitudinal approach to study of biological and cognitive change with Latent Growth Curves models that allow estimation of the shape of the trajectories of aging. Aim 6. Methodological contributions. During the proposed extension award period, we plan to initiate several methodological investigations, in which we will compared manual volumetry and ROI-based evaluation of white matter integrity with various semi-automated methods, with a hope to improve those methods to the level comparable with the "golden standard."